Recrystallization of Low Melting Point Metal Alloys
in Microgravity
Team Name: 2004-2005 University of Minnesota Microgravity
Research Team - Solid Mechanics
Institution:
University of Minnesota – Twin Cities
Aerospace Engineering and Mechanics Department
107 Akerman Hall
117 Union St SE
Minneapolis, MN 55455
Team Contact:
Jeremy Hanke (hank0072@umn.edu)
(920)-819-6127
Faculty Supervisor:
Dr. Thomas Shield shield@aem.umn.edu
(612)-626-7793
Team Members:
Hanke, Jeremy
(hank0072@umn.edu).
Flyer / Senior / Aerospace Engineering
Stephani, Kelly (step0206@umn.edu)
Alt. Flyer / Senior / Aerospace Engineering
Plumbo, Reid
(plum0047@umn.edu)
Flyer / Senior / Aerospace Engineering
Vue, Fue
(vuex0046@umn.edu)
Flyer / Senior / Aerospace Engineering
Gunderson, Matt (gund0199@umn.edu)
Flyer / Senior / Aerospace Engineering
Signed: ______________________________
Thomas Shield
Faculty Advisor
Date: __________
Table of Contents
Page No.
I.
II.
Technical Description
a. Flight Week Preference
b. Abstract
c. Test Objectives
d. Test Description
e. References
2
2
2-3
3-4
5
Experiment Safety Evaluation
6-12
III. Outreach Plan
a. Outreach Objectives
b. Outreach Phases
i. Website
ii. School Visits
iii. Research Community
iv. Media Outreach
v. University of Minnesota
IV. Administrative Requirements
a. Institution’s Letter of Endorsement
b. Statement of Supervising Faculty
c. Funding/Budget Statement
1
13
13
13
14
14
14
15
16
17
I. Technical Description
1.1 Flight Week Preference:
Our team’s top three preferences for flight week are listed below.
1. Flight Group 3 – March 31 - April 9, 2005
2. Flight Group 4 – April 18 – April 22, 2005
3. Flight Group 1 – March 3-12, 2005
1.2 Experiment Abstract:
This experiment aims to evaluate the differences in metal alloy crystal structures
when the material solidifies in a reduced gravity environment as opposed to typical Earth
gravity conditions. As NASA and other space-going organizations push for longer and
more demanding space missions, the need to be able to fabricate or manufacture tools and
other apparatus during the mission is becoming evident.
Little is known about how a reduced gravity environment affects the resulting
molecular structure and characteristics of a metal alloy. This experiment will use the
metal alloy Cerrobend®, which has a melting point of 158°F, to test this phenomenon.
Using an alloy with a low melting point is important to ensure the safety of the
experiment. Samples of Cerrobend® will be melted by sending an electric current
through the alloy. The sample will then be allowed to solidify within an enclosed
environment in reduced gravity. These reduced gravity samples will be analyzed and
compared with samples created in a normal gravity environment to determine any
difference in crystal structure. A hardness test will also be performed on both sets of
samples.
1.3 Test Objectives:



Determine an efficient, safe and effective method to melt and solidify a
specimen within a short period of reduced gravity.
Determine how a reduced gravity environment affects the internal crystal
structure of a solidifying metal alloy.
Evaluate how material hardness differs in alloys crystallized in
microgravity to that of samples made in terrestrial gravity conditions.
2

Study the solidification of an alloy in an environment where the
intermolecular attractions are the primary forces involved to learn more
about the mechanics of re-crystallization.
 Determine how the results from this experiment can be used to advance or
benefit science and technology and/or society.
This experiment is not a follow-up to any previously flown experiments.
Hypothesis:
Due to a lack of gravitational forces, the dynamics involved in recrystallization
will be slightly altered, and thus a change in the resulting crystal structure is expected.
Unlike in a terrestrial gravity environment, there will be no convective forces due to
gravity. This team hypothesizes that convective flow has an observable effect on the
physical and mechanical properties of metal alloys, as shown in previous similar studies
(Hayakawa et al. 1).
1.4 Test Description
In this experiment, the alloy Cerrobend® will be flash melted and solidified in
both a terrestrial laboratory environment (where the gravitational force g = 9.8 m/s2 or
32.2 ft/s2), as well as in a microgravity laboratory environment. The goal of this study is
to determine how the absence of gravity affects the crystallographic structure and the
physical properties of an alloy.
A portable laboratory station (PLS) will be utilized for both terrestrial
testing (Phase I) and for microgravity testing (Phase II). The execution of this
experiment will begin months prior to the flight. The team will establish a means for
comparison by performing the experiment in the PLS on the ground. Samples of
Cerrobend® will be cast with wires securely set into opposite sides of the samples. Each
assembly will be placed into a fully enclosed cubic Lexan® chamber. The four inner
chambers will be bolted to a tray that can be slid in and out of an outer safety chamber.
The approximate size of the inner chambers and outer chamber is one cubic foot and 37.7
cubic feet, respectively. Both inner and outer chambers are constructed from Lexan®
with sealed edges. Note that there will be one sample of Cerrobend® per inner chamber.
Wires will be electrically connected and integrated into a circuit consisting of a switch,
fuse and constant current source. The entire apparatus will consist of a row of
approximately 8 Lexan® chambers, each with its own on/off switch. This entire
apparatus will be fully enclosed by a large Lexan® chamber, with switches located on the
exterior of the PLS for use by the experimenters.
When the set-up and safety check are complete, the large chamber will be closed
to begin the flash melting process. The first switch will be turned to the “on” position
and approximately 10 Amperes of current will pass through the specimen. Current will
be provided until the alloy is melted. To assist in the cooling process, compressed air
will be circulated though a single cooling coil. This coil will be immersed in a separately
contained ice bath. The cool air will then be circulated throughout the PLS, which will
3
increase the rate of solidification. The alloy will cool, recrystallize inside the chamber,
and the sample will be stored for further analysis. This process will repeat until all
specimens are flash melted and recrystallized. The same process will be used during the
microgravity portion of the experiment. The design of the experiment allows for most of
the set-up and preparation to be completed and checked prior to flight, allowing the
experimenters to focus on the task at hand.
After the samples from both Phases I and II are collected, the specimens will be
qualitatively analyzed. Each sphere will be cut in half, and one half of the sphere will be
placed under a microscope to observe the crystalline structure formed during
solidification. The other half will be polished and will undergo a Brinell hardness test.
The results from both of these analyses will be recorded. The team will then compare
data gathered from Phase I and II.
Results from experiments aboard the United States Microgravity Payload (USMP)
mission series support our thesis. Principle Investigator Martin Glicksman of Rensselaer
Polytechnic Institute led the Isothermal Dendritic Growth Experiment (IDGE) (UMSP-4
7). The purpose of IDGE was to study the effects of microgravity on the formation of
dendrites. Dendrites are “…tree-like crystals with branches and sub-branches emerging
from the main stem (UMSP-4 7).” Dendritic formation on earth is unlike dendritic
formation under reduced gravity conditions. A dendrite crystal formed on earth has no
branches grown off the top end. The same crystal formed in a microgravity environment
will experience branch growth throughout the entire structure. This is caused by
“…convective flows that cause the top and the bottom of the branch to solidify
differently. In microgravity, dendritic growth is symmetrical (UMSP-4 8).” This
“…buoyancy-driven convective flow, which is the motion of the molten material caused
by gravity acting on the sample, affects the dendrites (UMSP-4 8).”
Since convection affects the motion of molten material in general, Cerrobend®
will likely be affected by this phenomenon during this experiment in Phase I. The team
hypothesizes that convective flow has a qualitatively measurable effect on the physical
properties of Cerrobend®. The absence of convection will allow a more freely arranged
crystal structure. Because of the less restricted arrangement, atoms will naturally form
stronger bonds with other atoms to which they are highly attracted. Convective flow
causes atoms to form weaker bonds because they were forced together. The net increase
in stronger bonds between atoms suggests that a metal alloy solidified in microgravity
conditions will be physically different from the same alloy solidified on earth. The
difference in physical properties may be observed by performing a Brinell hardness test
on each specimen.
It is evident that the essence of this experiment requires a reduced gravity
environment. Microgravity is essential in order to determine gravitational influence on
the recrystallization of Cerrobend®.
After conducting this experiment, this team hopes to have attained three goals:
1) Determine an efficient, safe and effective method to melt and solidify a specimen
within a short period of reduced gravity.
2) Compare the similarities and differences of the Cerrobend® crystalline structure
when solidified in a terrestrial environment and a reduced gravity environment.
3) Determine how the results from this experiment can be used to advance or benefit
science and technology and/or society.
4
References:
Hayakawa, Yasuhiro, et al. “Study on the Crystallization of InGaSb under Different
Gravity Conditions.” Shizouka University.
<http://www.space.gc.ca/asc/pdf/2000_Hayakawa.pdf >.
“UMSP-4: The Final Round of a Great Series.” Microgravity News 4.3 (Fall 1997).
<http://microgravity.msfc.nasa.gov/mgnews/fall97/lead.html>.
United States. National Aeronautics and Space Administration. Educational Brief: A
NASA Recipe for Protein Crystallography.
<http://spacelink.nasa.gov/Instructional.Materials/NASA.Educational.Products/R
ecipe.for.Protein.Crystallography/Protein.Crystallography.pdf>.
5
II. Experiment Safety Evaluation
2.1 Flight Manifest
Proposed Fliers:
Matt Gunderson
Jeremy Hanke
Reid Plumbo
Fue Vue
Alternate Flyer/Ground Crew:
Kelly Stephani
There is currently no journalist working with this team.
None of the team members have any previous NASA flight experience.
2.2 Experiment Description/Background
The objective of this team is to research the effects of reduced gravity on the
crystal structure growth of metal alloys. When a metal is in its liquid state, no crystal
structure exists. Only when the sample cools and solidifies does a crystal structure form.
Each element of this crystal structure has mass and is therefore influenced by the effects
of gravity. This research will examine the crystal structure of an alloy formed under the
absence of these gravitational forces. This will be accomplished by melting and cooling a
small sample of Cerrobend® alloy with electric current while under microgravity
conditions. This is the first year this research has been offered from the University of
Minnesota @ Minneapolis; this is not a re-flight.
2.3 Equipment Description
To successfully melt and harden a sample of Cerrobend® in microgravity, it must
be quickly heated and cooled. The alloy selected for this experiment has a low melting
point of 160°F. In order to sidestep the problems associated with the heating and
containment of a reservoir of molten Cerrobend®, this team intends to use electricity.
Current will flow from a constant current source at a level of approximately 10 Amperes
through a prefabricated plug of the alloy. The wires passing this current to the sample
will be pre-molded into the metal before arrival at Ellington Field. The resistance
intrinsic to the metal will cause heating and the sample will melt. This technique of flash
melting negates the need to contain excess liquid metal and allows the experiment to be
performed on a “by-sample” basis. This method also contains a unique safety feature;
when the solid sphere turns to liquid and detaches from the wires, the electrical circuit is
automatically broken. This is similar to most fuse technologies. Alternative fuses will be
be installed to prevent sudden large current discharges. When the sample has fully
6
melted, a manually operated switch will open the circuit carrying the current and the
metal will begin to cool. The cooling process, and possibly the melting process, will take
place in microgravity. All of this will happen within a small Lexan® box completely
isolated from the rest of the airplane. The cooling process will be helped by the
circulation of compressed air through a single cooling coil. This coil will be immersed in
a separately contained ice bath. When the air moves through the coils, it will cool below
ambient temperature and help speed the solidification process. This is important as the
sample must fully solidify in microgravity in order to obtain meaningful results.
Switches
Individual
Containment Box
Alloy Sample
Constant Current
Source
Ice Bath and
Cooling System
Figure 1: Portable Lab Station and Test Setup Schematic
2.4 Structural Design
The main structure of this test apparatus is composed of Unistrut® tubing that
forms a box measuring 62” x 21” x 50”. This primary structure will be recycled from the
2004 University of Minnesota @ Minneapolis team. This framework will be strapped to
7
the C-9 floor taking advantage of the onboard cargo straps. Inside the steel frame resides
a Lexan® box that fills the entire volume of the outer steel structure. This is the primary
test chamber. The primary test chamber is bolted to the primary structure and a siliconebased glue will seal the edges. This is necessary to keep gaps and orifices to a minimum
to reduce the risk of molten metal at 160°F from escaping into the cabin should one of the
secondary test chambers fail. The secondary test chambers are also made from Lexan®
with sealed edges. These inner chambers, where the actual melting will occur, will
measure 12” x 12” x 12”. The team currently plans to encapsulate approximately 8 test
chambers inside the primary test chamber. Each of these chambers will be identical in
construction, but may vary in either testing methods or materials. The test chambers will
all have a toggle switch accessible from the outside that controls the current flow to the
sample. In line with this switch will be a fuse that shall prevent sudden, excessive current
spikes.
Component
Unistrut® frame with Lexan® walls
Secondary Lexan® test chambers
(including switches, fuses etc.)
Constant Current Source
Laptop computer
Data logging equipment
Cerro Alloy spheres to be melted
Estimated Weight
120 lbs.
25 lbs.
25 lbs.
10 lbs
10 lbs
1 lb.
Total Weight Estimate: 194 lbs.
2.5 Electrical System
The electrical requirements for this research are minimal. The major sink of
power will be the constant current source. This piece is essential to the experiment as it
allows the melting of a sample without the use of flame or other hot materials. The team
estimates that 10 Amperes will be required to melt the samples quickly. This is an
estimate attained through basic power and resistivity calculations. We will
experimentally determine the exact current requirements prior to flying the experiment.
The team also plans to bring aboard a laptop computer for data logging purposes. A
standard laptop computer requires 110VAC power at 60Hz if available. The laptop
battery may also be used if the required power is unavailable.
Component
Constant current
supply
Laptop computer
Use
Provide current to
melt sample
Data logging
Voltage, Frequency
110VAC, 60Hz
Current Required
10A
110VAC, 60Hz
1.2A
The electrical requirements remain the same for ground testing. A schematic of the
electric circuit for the experiment is shown in Figure 2.
8
Constant
Current
Source
Fuse
Switch
Test Box
Alloy Sample
Figure 2: Electrical Circuit Schematic
2.6 Pressure/Vacuum System
The only pressure mechanism used in this experiment involves the compressed air
system used for cooling. The team would like to use pressurized air from the C-9 if it is
available. The cooling system will exhaust freely into the PLS. The box itself is vented
to the atmosphere and the air jet system will not result in any appreciable pressure
increase in the box.
2.7 Laser System
There are no lasers used in this experiment.
2.8 Crew Assistance Requirements
No assistance from the crew is anticipated to complete this experiment successfully.
2.9 Institutional Review Board
This experiment contains to biological substances or human test subjects. This
experiment will not require an IRB review.
9
2.10 Hazard Analysis
Event
Molten metal at
160°F escapes
test chamber
Cause
-Failure of test chamber
structure
-Failure of seals on test
chamber
Electrocution
-Contact with bare
wires
Repercussions
-Burns (after 1
second of contact)
-Temporary
blindness (if eye
contact)
-Damage of nonmetal aircraft
interior
-Death
-Incapacitation
Fracture of
Lexan®
containers
-Impact of free floating
object
-Excessive stresses
from flight conditions
-Injury to
experimenters/flight
crew
-Damage to cabin
Impact with
sharp
edge/corner
Stowage
Restraint Failure
-Sharp edges or corners
-Bodily harm
-Failure of tie-down
straps
-Bodily harm
-Damage to cabin
-Damage to PLS
Inhalation of
alloy fumes
-Overheating of alloy
-Overexposure to
AND concurrent failure harmful alloy
of test chamber
elements
10
Precautions Taken
-Molten samples
will be within
secondary test
chambers inside the
primary test
chamber
-All interaction with
electricity is done
through toggle
switches; wires are
insulated and
contained within
primary and
secondary test
chambers
-Gloves will be
worn for any
interaction with
electrical
components
-High safety factor
of structure makes
this possibility
highly unlikely
-All sharp edges and
corners will be
covered in padding
-Load analysis will
be performed to
ensure adequate
straps are used
-Electric circuit will
be broken once
alloy is melted
-Primary and
secondary test
chambers for
containment
2.11 Tool Requirements
Tools brought aboard the airplane
1 Straight and Phillips screwdriver
1 Leatherman or equivalent multi-purpose pliers
1 pair of leather gloves per experimenter
Tools that remain on ground
1 Ratchet and Socket set
1 Set of box end wrenches
1 Extra cargo strap
Extra cable ties
Each tool will be marked with our team and school name. Each tool will have a team
member responsible for its control and safekeeping.
2.12 Ground Support Requirements
No ground support services are required for this experiment.
2.13 Hazardous Materials
There are no toxic, corrosive, explosive or flammable materials used in this experiment.
2.14 Procedures
Ground Operation:
We will verify the proper working of all experiment components upon arrival in
Houston. This may include some assembly of the PLS and test boxes after transport.
Once the PLS and all apparatus are properly assembled, we will ensure that the
experiment functions as planned prior to flight date.
Pre Flight:
The team will install the test package on the airplane using the cargo straps
already on the C-9 aircraft. All necessary electrical connections will be made at this time.
The laptop and constant current sources will be plugged in. The constant current source
will be switched to the “off” position and will not be turned on until the moments before
the first period of weightlessness. Each of the inner test chambers will be loaded with its
metal alloy and the main test chamber will then be shut and locked into place. It is the
11
hope of the team that this lock will be accessible in flight to retrieve spent samples and
swap in new samples from the inner test chambers.
In Flight:
Just prior to the period of weightlessness, the constant current source will be
turned on and shall be ready to deliver the requisite 10 Amperes. When the C-9 enters the
flight path that simulates weightlessness, the first switch on the first test chamber will be
turned to the “on” position. The provided compressed air will be circulated through the
cooling system and into the PLS. The sample will cool and when the C-9 begins to climb
again, the sample will fall to the bottom of the chamber where it will remain until all the
other samples have been processed. When all 8 samples have been used, the box will be
opened during either the climb phase, or a period of weightlessness. The used samples
will be collected and replaced with fresh ones. These samples will be placed in a sealed
box attached to the test package. This procedure will then be repeated.
Post Flight:
When the flight is completed and the airplane has safely landed, the constant
current source will be switched off and unplugged. The laptop will also be switched off
and unplugged. The samples will be collected from the previously mentioned container
and preserved for further study. When the team returns home to Minnesota, the samples
will be cut apart and their crystal structure will be analyzed. The team also hopes to
characterize the physical properties and compare them to that of a sample recrystallized
under the influence of gravity. This experiment is different in that most of the meaningful
science will take place away from Ellington Field. Preparation for the second flight will
include a full debrief by the first team of flyers. Successes and failures will be shared in
hopes that the second team of flyers can expand on the triumphs of the first. Adjustments
to the test package will be made based on the suggestions of the first team. One of the
goals of this year’s research is to develop the techniques that future teams can use to
obtain consistently good results.
12
III. Outreach Plan
3.1 Outreach Objectives
Being involved in this exciting research project is not only a great experience for
the members of the team, but will provide our team with a great opportunity to showcase
the possibilities in science to younger students and the general public. The team hopes to
get students excited about the opportunities in science and engineering fields by
presenting our research to schools. We also hope to reach out to the local media in order
to expand our outreach audience to a wide variety of people.
3.2 Outreach Phases
Website:
The team has already created and uploaded a website for our project, which can
be found at http://www.aem.umn.edu/proj-prog/sfo/materials-2005/. The team will soon
purchase the domain name http://www.floatinggophers.org in order to make our site more
accessible. The site will be updated to reflect the progress of the team as we move from
initial experiment design to testing and finally to our trip to Houston. Information about
the team members is available, and links to other sites for more information will be added
throughout the year. We hope to use the website to advertise our outreach program and
to provide an easy spot to locate information that we collect.
School Visits:
The team plans to make visits to several schools in the spring to showcase our
findings and experiment. Several schools around the Twin Cities will be contacted, as
well as some of the team members’ alma maters in Wisconsin and Minnesota. Schools
that we plan to contact include:
 Wausau West High School - Wausau, Wisconsin
 Trinity Lutheran School – Wausau, Wisconsin
 Bethany Academy – Bloomington, Minnesota
 St. Mary’s Springs – Fond du Lac, Wisconsin
 Apple Valley High School – Apple Valley, Minnesota
 Echo Park Elementary School – Burnsville, Minnesota
The main target audience will be middle school and early high school students
because we feel that making an impression at that age has a greater impact. These visits
will show students the exciting aspects of the field of science. By sharing our
experiences in testing aboard the C-9 aircraft in zero gravity, we hope to show that
engineering and research are much more than sitting around a lab staring at test tubes.
Additionally, we hope to impress upon the students that many of the best experiences to
13
be had in college and in life require student initiative, like this microgravity project.
Getting students to motivate themselves is perhaps the most important lesson that can be
learned to prepare them for life after high school.
Technical Journals:
Although a major motivation for our team in pursuing this project is for the
experience itself, we hope to provide results that are of real value to the academic
community at large. As such, we hope to pursue journals and technical publications to
publish our findings, such as International Journal of Solids and Structures, Journal of the
Mechanics and Physics of Solids, and Scripta Materialia. Sharing our research with
others in the field is an important facet of the research process.
Media Outlets:
The team plans to involve the local media with our project to spread the word
about the program and the University of Minnesota’s Aerospace Engineering
Department. We will seek to use various media outlets to distribute our story, including
the University’s own Minnesota Daily, the Minneapolis Star-Tribune, local television
stations such as KARE 11, KSTP and KMSP, as well as the local National Public Radio
affiliate, KNOW. It is important to share that students can have valuable experiences
with running their own research project and the creative processes that are involved in
that. Through these media outlets, we will be able to reach a large audience who we hope
will then visit our website to learn more about the project.
At the University of Minnesota:
We will outreach to others within our own department at the University of
Minnesota. We hope to speak to students in some of the freshman and sophomore level
courses to pique their interest in both the NASA Reduced Gravity Flight Opportunities
Program offered here and the Aerospace Engineering Department as a whole. We also
may make presentations to the University’s chapter of AIAA and other professional
societies. By making sure that students are informed about the opportunities available to
them, we hope to ensure that the microgravity program here at the University of
Minnesota remains an exciting and rewarding experience for students.
14
IV. Administrative Requirements
15
4.2
Statement of Supervising Faculty
As the faculty advisor for an experiment titled “Recrystallization of Low Melting
Point Metal Alloys in Microgravity” proposed by a team of undergraduate students from
the University of Minnesota – Twin Cities campus, I concur with the concepts and
methods by which the experiment will by conducted. I will ensure that all reports and
deadlines are completed by the student team members in a timely manner. I understand
that any default by this team concerning any Program requirements (including
submission of final report materials) could adversely affect selection opportunities of
future teams from the University of Minnesota – Twin Cities.
Signed,
Date:
Dr. Thomas Shield
16
4.3 Budget and Funding
The costs of travel and equipment will be provided by a combination of the Aerospace
Engineering and Mechanics Department of the University of Minnesota and the
Undergraduate Research Opportunity Program (UROP) at the University of Minnesota.
Equipment itself will either be provided or purchased.
Equipment Expenses
Constant Current Supply
$500
Plexiglass for test boxes and test stand
$100
Cerro Alloys for test material
$65
Bolts, Fasteners, Misc.
$40
Shop Labor
$250
Electrical Switches and Wires
$50
Miscellaneous Structural and Electronic Components
$600
Total Estimated Equipment Cost =
$1605
Travel Expenses
Hotel Accommodations: 5 people, 14 nights, $140 per night
$1960
Food: 5 people, 14 days, $25 per person per day
$1750
Transportation: 5 people, roundtrip airfare, Car Rental, $500 per person
$2500
Shipping: Experiment both ways
$800
Proposal Copies (Publications)
$100
Total Estimated Travel Cost =
17
$7110